1. Field of the Invention
The present invention relates to control of oil or gas well production in the latter stages of well life and, more particularly, to a device and method for controlling the action of a cluster of oil and or gas wells that are sharing a production line or sales line while using a plunger lift system or an oil lift system; generally, any artificial lift system.
2. Description of the Related Art
In many oil and gas well fields with artificial lift system production installations the well flow lines or sales lines are connected through a common manifold. Flow lines, sales lines and the common manifold are all interconnected and are collectively known as the sales line. Each well head is separated by a valve; commonly know as the motor valve. They also typically share a sales meter, fluid storage tanks, and separator. This arrangement is known as a well battery. At present in order to produce from these wells, controllers have been developed to synchronize the well flow and cycle timing. These systems turn on each well in sequence, allowing them to flow for a set period of time and then disabling them until all other wells in the well battery have run in order. There is no communication or connection between each well in the system, rather the synchronization depends on accurate clocks in each controller. There are at least two reasons for this cautious approach. First, not all wells in the well battery produce with the same formation pressure. It is therefore possible for stronger wells (wells with higher formation pressure) to completely stop production from other wells attached to the common manifold. The effect of this can be disastrous as the wells will load up with fluid and fail to produce until the fluid has been removed by swabbing. Second, the flow meter can be overrun with more than one well flowing, and the pressure at the separator can be too high.
The present state of the art for electromechanical control systems in the oil and gas recovery industry can be seen in U.S. Pat. No. 5,427,504 (plunger only), U.S. Pat. Nos. 4,921,048, 4,685,522, 4,664,602, 4,633,954 and 4,526,228. Also U.S. Pat. No. 6,634,426 describes the determination of plunger location and well performance parameters in a borehole plunger lift system. The following two patents describe using a single micro controller connected to all wells in a well battery, and using timing to control when motor valves open; U.S. Pat. No. 4,685,522, entitled “Well production controller system”, and U.S. Pat. No. 4,921,048, entitled “Well production optimizing system”. These patents do not describe a system like the present invention that uses pressure spike detection in a sales line, to control when a motor valve opens. All of these patents are incorporated herein by this reference.
The synchronization method is an inefficient way of producing oil and gas from these wells, because, there are large periods of time when no oil and or gas is flowing to the common manifold. Also the stronger wells are not allowed to produce to their full capacity. Furthermore, the system described in U.S. Pat. No. 4,685,522 has the disadvantage of requiring sensor and power cables from each wellhead to a central controller. These cables sometimes extend to distances of over 700 yards, and usually must be buried in the ground.
Further, the synchronization method does not allow for changes in well and sales line conditions. This invention provides a solution to these problems.